High wildfire damage in Interface communities in California

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Globally, and in the US, wildfires pose increasing risk to people and their homes. Wildfire management
assumes that buildings burn primarily in the wildland–urban interface (WUI), where homes are either ignited directly
(especially in intermix WUI areas, where houses and wildland fuels intermingle), or via firebrands, the main threat to
buildings in the interface WUI (areas with minimal wildland fuel, yet close to dense wildland vegetation). However, even
urban areas can succumb to wildfires. We examined where wildfire damages occur among urban, rural and WUI (intermix
and interface) areas for approximately three decades in California (1985–2013). We found that interface WUI contained
50% of buildings destroyed by wildfire, whereas intermix WUI contained only 32%. The proportion of buildings destroyed
by fires among classes was similar, though highest in interface WUI areas (15.6%). Our results demonstrate that the
interface WUI is where most buildings were destroyed in California, despite less wildland fuel. Continued advancement of
models, mitigation and regulations tailored for the interface WUI, both for California and elsewhere, will complement the
prior focus on the intermix WUI.